Title: Power unit and cartridge, and fuel cell system comprising power unit and cartridge

Abstract: A power unit, a fuel cartridge, and a fuel cell system having the power unit and the fuel cartridge. The power unit includes a coupling unit to couple with the fuel cartridge. The coupling unit includes a nozzle that receives fuel supplied from the fuel cartridge, a selection key to selectively mate with the fuel cartridge, and an outer unit surrounding the nozzle. An end of the nozzle is located between the selection key and an end of the outer unit.